BERLIN (Reuters) - Overfishing partly caused by booming
demand for shark fin soup, a delicacy in some Asian countries,
is threatening the existence of 11 kinds of ocean sharks, an
international study showed on Thursday.

The fish, often seen as ferocious sea predators, suffer
from largely unregulated fishing for their valuable fins, said
the report into 21 species of sharks and rays living in the
open oceans.

The experts who wrote the study, organized by the
International Union for Conservation of Nature, also urged
governments to quickly impose catch limits.

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"The traditional view of oceanic sharks and rays as fast
and powerful too often leads to a misperception that they are
resilient to fishing pressure," Sonja Fordham, report co-author
and deputy head of the IUCN's shark specialist group, said.

Thresher sharks, silky sharks and the shortfin mako are all
under threat, said the report, presented at a May 19-30 U.N.
biodiversity conference in the city of Bonn.

The sharks, all "pelagic" or living in the open ocean,
include large species such as the whale shark and great white
shark. Although relatively few compared to coastal and deep sea
sharks, a greater number of pelagic species is under threat.

"The increase in demand for shark fin soup in countries
like China is a major driver of the problem," Fordham told
Reuters, noting that growing affluence in China, where the soup
is served as a treat at celebrations, is behind its increasing
popularity.

Fishers from all over the world catch and trade sharks for
their lucrative fins, often discarding their carcasses, said
Fordham, noting Indonesia and Spain are among the top culprits.

Seven ocean pelagic shark species will be added to the IUCN
2008 "Red List" of endangered species, bringing the total to
21.

Sharks and rays are especially vulnerable as they take many
years to reach sexual maturity and have few offspring.

Research shows the disappearance of shark species could
lead to the demise of other species by upsetting the natural
balance in the world's oceans.

Governments should set up catch limits for sharks and rays
and ensure an end to shark finning, said the report. It also
recommended a better monitoring of fisheries, more investment
in research and closer international cooperation.

"Humans are making increasing use of ocean resources so
many more aquatic species, particularly sharks, are coming
under threat," said Nicholas Dulvy, lead author of the study
published in "Aquatic Conservation: Marine and Freshwater
Ecosystems."

"But it doesn't have to be like this. With sufficient
public support and political will, we can turn the tide."